1. Field of the Invention
This invention relates to a toner used in recording processes utilizing electrophotography, electrostatic recording, magnetic recording or toner jet recording.
2. Description of the Related Art
A number of methods are conventionally known as methods for electrophotography. In general, copies or prints are obtained by forming an electrostatic latent image on an electrostatically charged image bearing member (hereinafter also termed “photosensitive member”) by utilizing a photoconductive material and by various means, subsequently developing the latent image by the use of a toner to form a toner image as a visible image, further transferring the toner image to a recording medium such as paper as occasion calls, and then fixing the toner image onto the recording medium by the action of heat and/or pressure. Apparatus for such image formation include copying machines, printers and so forth.
These printers or copying machines are being changed over from analogue machines to digital machines, and it is strongly sought to have a good reproducibility of latent images and a high resolution and at the same time to be made high-speed and reduce power consumption in their use. Here, take note of printers, for example. The proportion of power consumption in the fixing step is fairly large in respect to the total power consumption, and hence the power consumption may increase with a rise in fixing temperature. A high fixing temperature may also cause problems such as curl of image-printed paper after fixing. Accordingly, there is a great desire for making fixing temperature lower.
Meanwhile, there is also a great desire for on-demand performance in printers and copying machines, and, in recent years, what is called a film fixing assembly and a magnetic induction type fixing assembly have been brought forth. These fixing assemblies have a very good on-demand performance. However, it is the case that, compared with conventional heat roller type fixing assemblies, pressure is applicable with difficulty to make the fixing performable with greater difficulty.
Further, printers need to deal with a variety of recording materials, and hence there is a great desire for a toner having a good fixing performance in a broad temperature region. Also, the printers or copying machines, which are sought to reduce power consumption, are on the other hand being made more high-speed, where the toner is also required to be improved in running stability.
To cope with the above, many studies have been made on how toners are made fixable at a low temperature, and it is reported that the use of a polyfunctional ester wax enables improvement in low-temperature fixing performance (see Japanese Patent Laid-open Applications No. 2000-019768 and No. 2006-098745 and International Publication WO98/20396).
A toner is also proposed which makes use of a polyfunctional ester wax having a specific solubility in styrene monomers and a specific molecular weight, and it is reported that the toner has superior low-temperature fixing performance and images with a high resolution are obtainable (see International Publication WO01/01200 and Japanese Patent Laid-open Application No. 2001-147550).
It is further reported that the use of two types of waxes in combination enables improvement in low-temperature fixing performance (see Japanese Patent Laid-open Applications No. H11-218960, No. 2002-072540 and No. 2002-072546).
However, even with use of such toners, it has not well been succeeded in achieving both the on-demand performance and the low-temperature fixing performance, and it has been insufficient to be adaptable to high-speed processing. Moreover, there has been room for much further improvement also in respect of image stability during long-term service.